1. Field of the Invention
The present invention relates to a lubricant for a magnetic recording medium, a magnetic recording medium, a manufacturing method of a magnetic recording medium, and a magnetic recording and reproducing device.
Priority is claimed on Japanese Patent Application No. 2014-005852, filed Jan. 16, 2014, the content of which is incorporated herein by reference.
2. Description of Related Art
Currently, track density of a magnetic recording medium reaches 400 kTPI. When recording is performed with respect to both surfaces of one disk of 65 mm, the magnetic recording medium can records 500 GB. Further, recording density of a magnetic recording and reproducing device is continuously improving. In order to improve the recording density of the magnetic recording and reproducing device, it is most important to reduce a distance (space loss) between a head sensor portion and a recording material of the magnetic recording medium. For this reason, protective coating of a head and medium thin, and decreasing a flying height of the head have been ongoing consideration. It is understood that a thickness of a lubricant coated on the protective layer is effective in term of the space loss, and thus an approach for coating the lubricant extremely thin has been ongoing.
In general, in the magnetic recording medium, a recording layer, a protective layer such as carbon, and a lubricant layer are formed on a substrate for a magnetic recording medium in this order. The protective layer protects information recorded on the recording layer, and increases slidability of a magnetic head. However, by only disposing the protective layer on the recording layer, durability of the magnetic recording medium is not sufficiently obtained.
For this reason, in general, the lubricant layer is formed by coating the lubricant on a front surface of the protective layer. By disposing the lubricant layer on the protective layer, it is possible to prevent the magnetic head of the magnetic recording and reproducing device from being directly in contact with the protective layer, and it is possible to considerably reduce a friction force of the magnetic head sliding on the magnetic recording medium. Therefore, durability is improved.
As the lubricant used in the magnetic recording medium, a perfluoropolyether-based lubricant or the like has been proposed. For example, in Japanese Unexamined Patent Application, First Publication No. S62-66417, a magnetic recording medium which is coated with a lubricant of perfluoroalkyl polyether having a structure of HOCH2—CF2O—(C2F4O)p—(CF2O)q—CH2OH (p and q are integers) is disclosed.
In Japanese Unexamined Patent Application, First Publication No. H09-282642, a magnetic recording medium which is coated with a lubricant of perfluoroalkyl polyether (tetraol) having a structure of HOCH2CH(OH)—CH2OCH2CF2O—(C2F4O)p—(CF2O)q—CF2CH2OCH2—CH(OH)CH2OH (p and q are integers) is disclosed.
In Japanese Unexamined Patent Application, First Publication No. 2006-131874, a lubricant in which at least one type of spherical cage-type molecule selected from fullerene and a derivative thereof, and at least one type of fluorine-based lubricant, preferably a perfluoropolyether-based compound are mixed is disclosed.
In Japanese Unexamined Patent Application, First Publication No. 2013-170137, a fullerene derivative having a perfluoropolyether group on a terminal is disclosed.